TP&N sub feed

[Engineer54]

I've already purchased a 100a 4 pole hager MCB, 15kA, only problem being its a 4 pole MCB so the neutral will be fused if used in one of the poles, anyone see this as a problem? If this breaker disconnects, all the phases will be out

If the neutral breaker element is clearly marked with an ''N'' or Neutral it will have compensated making and breaking. It may also just be an isolator (switch)... My advice would be to check with the manufacturer if uncertain on the functioning of the device you have purchased...

What if the neutral disconnects first? Is a four pole a good idea?

Highly unlikely, and if it did, then something would be very wrong anyway... lol!!!

 

[electric will]

Oh well

 

[TPES]

If the neutral breaker element is clearly marked with an ''N'' or Neutral it will have compensated making and breaking. It may also just be an isolator (switch)... My advice would be to check with the manufacturer if uncertain on the functioning of the device you have purchased...

It is a 4 pole MCB with every pole fused exactly the same, there is no N or neutral markings on it..

 

[TPES]

Google Hager HMD490T

That's what I have

 

[spark 68]

Deleted

 

[TPES]

Deleted

??????

 

[electric will]

Back to my post about the neutral possibly disconnecting before the phases in some types of isolators, some isolators are made so the neutral disconnects last but I'm unable to find the spec of them, just for interest really?
Any one know the rating and would be kind enough to help me out?

 

[High Tower]

If its a mcb the disconnection should be harmonious.........no?

 

[Amp David]

^^^ what I was thinking too

 

[electric will]

I thought this was the reason why a lot of isolators in TP+N boards don't isolate the neutral, unless its the main point of isolation?

 

[TPES]

It's the main point of isolation for the sub board I'm installing..

 

[electric will]

I mean the main point to the whole installation

 

[Marvo]

Gawd you're in a minefield with late break contacts. You'd also need the contact to be early make as well if it's for the neutral. I would stick with a device that's rated for isolation of a 3ph and N supply, a device with one of the poles designated specifically as neutral that way the make/break timings should be correct.

 

[electric will]

Marvo, so this is already built into the isolator, as long as you use the neutral pole for the neutral obviously?

 

[Marvo]

Yes, if it's designed as a 3ph +N isolator then the pole that's designated specifically as 'N' should be late break / early make. That said if it's a no-name or bargain basement brand I'd want to check the manufacturers specs myself, in fact if it was being used in a critical application I'd probably connect the supply and my data logger to the load side and check it for myself with the customers load off-line first.